Method of manufacturing semiconductor elements

Abstract

A method of manufacturing semiconductor elements includes: disposing a semiconductor layer made of a nitride semiconductor on a first wafer; and bonding a second wafer to the first wafer via the semiconductor layer. The first wafer has an upper surface including a first region and a second region surrounding a periphery of the first region and located lower than the first region. In a top view of the first wafer, a first distance between an edge of the first wafer and the first region of the first wafer in each of a plurality of first directions parallel to respective m-axes of the semiconductor layer is smaller than a second distance between the edge of the first wafer and the first region of the first wafer in each of a plurality of second directions parallel to respective a-axes of the semiconductor layer.

What is claimed is: 
     
       1. A method of manufacturing semiconductor elements, the method comprising:
 disposing a semiconductor layer made of a nitride semiconductor on a first wafer; and 
 bonding a second wafer to the first wafer via the semiconductor layer; 
 wherein the first wafer has an upper surface that includes a first region and a second region surrounding a periphery of the first region and located lower than the first region, 
 wherein, in a top view of the first wafer, a first distance between an edge of the first wafer and the first region of the first wafer in each of a plurality of first directions passing through a center of the first wafer and being parallel to respective m-axes of the semiconductor layer is smaller than a second distance between the edge of the first wafer and the first region of the first wafer in each of a plurality of second directions passing through the center of the first wafer and being parallel to respective a-axes of the semiconductor layer, 
 wherein the second wafer has a lower surface and an upper surface, the lower surface including a flat portion and an inclined portion surrounding the flat portion, the inclined portion inclining upward toward the upper surface, and 
 wherein, in said bonding the second wafer, the second wafer is bonded to the first wafer such that outer end portions of the first wafer located in the first directions are opposite to the inclined portion of the second wafer. 
 
     
     
       2. The method of manufacturing semiconductor elements according to  claim 1 , wherein outer end portions of the semiconductor layer in the first directions have a thickness greater than a thickness of outer end portions of the semiconductor layer located in the second directions. 
     
     
       3. The method of manufacturing semiconductor elements according to  claim 2 , wherein the first wafer comprises sapphire. 
     
     
       4. The method of manufacturing semiconductor elements according to  claim 2 , wherein the second region is located at least 2 μm lower than the first region. 
     
     
       5. The method of manufacturing semiconductor elements according to  claim 2 , wherein the second distance is in a range of 1 mm to 10 mm. 
     
     
       6. The method of manufacturing semiconductor elements according to  claim 5 , wherein the first distance is in a range of 0.1 mm to 5 mm. 
     
     
       7. The method of manufacturing semiconductor elements according to  claim 2 , wherein the semiconductor layer is disposed on the first region and the second region. 
     
     
       8. The method of manufacturing semiconductor elements according to  claim 2 , wherein the semiconductor layer is made of In X Al Y Ga 1-X-Y N (0≤X, 0≤Y, X+Y≤1). 
     
     
       9. The method of manufacturing semiconductor elements according to  claim 1 , wherein the first wafer comprises sapphire. 
     
     
       10. The method of manufacturing semiconductor elements according to  claim 9 , wherein the second region is located at least 2 μm lower than the first region. 
     
     
       11. The method of manufacturing semiconductor elements according to  claim 9 , wherein the second distance is in a range of 1 mm to 10 mm. 
     
     
       12. The method of manufacturing semiconductor elements according to  claim 11 , wherein the first distance is in a range of 0.1 mm to 5 mm. 
     
     
       13. The method of manufacturing semiconductor elements according to  claim 9 , wherein the semiconductor layer is disposed on the first region and the second region. 
     
     
       14. The method of manufacturing semiconductor elements according to  claim 1 , wherein the second region is located at least 2 μm lower than the first region. 
     
     
       15. The method of manufacturing semiconductor elements according to  claim 1 , wherein the second distance is in a range of 1 mm to 10 mm. 
     
     
       16. The method of manufacturing semiconductor elements according to  claim 15 , wherein the first distance is in a range of 0.1 mm to 5 mm. 
     
     
       17. The method of manufacturing semiconductor elements according to  claim 1 , wherein the semiconductor layer is disposed on the first region and the second region. 
     
     
       18. The method of manufacturing semiconductor elements according to  claim 1 , wherein the semiconductor layer is made of In X Al Y Ga 1-X-Y N (0≤X, 0≤Y, X+Y≤1).